Blocking the Bounce

Summer 2016

Photo of Sung Hoon KangWhen a rubber ball or block falls to the floor, it bounces.

Yet, recently, an architected rubber block made by mechanical engineer Sung Hoon Kang sat motionless when dropped.

The block’s lack of movement inspired Kang and his colleagues to further investigate the potential to alter energy absorption in architected materials. To do so, the team used computational modeling to determine the design elements of prototypes. A 3-D printer then interpreted the code to generate physical prototypes for testing.

After a couple of months, they hit on a winning formula—a new class of energy-absorbing materials, described in Advanced Materials by Kang, an assistant professor in the Hopkins Extreme Materials Institute; doctoral student Lichen Fang; and colleagues at Harvard.

Energy-absorbing materials are used widely for safety and protection purposes—for instance, to lessen the effects of a car crash or to safeguard fragile items in a shipped package. But existing energy-absorbing materials have shortcomings: Their performance degrades after use and/or they often rely on a specific load rate to absorb energy.

The new class of materials offers a viable solution. “The energy-trapping mechanism is reversible and repeatable,” Kang explains. “It’s also highly scalable, customizable, and independent of rate and loading history”—opening the door to many practical applications, from reusable car bumpers to better safety helmets.